Polyvinyl chloride (PVC) is widely used in both its rigid and flexible forms in applications, such as films, siding panels, window panels, sheets, fencing, decking, pipes and tubing. However, because rigid PVC is a hard and brittle thermoplastic polymer, it is often mixed with a modifier to form a composition that is less prone to failure on impact.
Chlorinated polyethylene (CPE) is used as an impact modifier component for rigid PVC compositions. In some cases, it is desirable for the CPE to be “bulk handleable,” meaning that it can be shipped in bulk trucks and/or stored in silos, with minimal agglomeration of the CPE over time. Normally, CPE cannot be handled this way, because it tends to block or mass, making it hard to get the CPE out of the truck, or silo, especially if it has been stored for any length of time. The blocking tendency of the CPE can be reduced by adding large amounts of antiblock agents, such as calcium carbonate, but this addition adds an extra processing step, which increases total costs, and also introduces the antiblock itself, which may not be desirable in the rigid PVC formulations. The addition of large amounts of antiblock agents can also lead to demixing and segregation of the individual components during transportation and/or conveying of the material. Another approach is to increase the molecular weight (and viscosity) of the CPE, but this leads to problems during the extrusion of the PVC formulation. For example, the use of excessively high molecular weight CPE in PVC can result in small specks or defects in extruded window profiles, which make such a product undesirable.
Conventional chlorinated polyethylenes containing high levels of residual crystallinity (for example >10 percent), such as for example, convention block chlorinated polymers, when used in a modified PVC composition tend to have reduced impact strength. Conventional randomly chlorinated polyethylenes, and especially the lower molecular weight (Mw<150,000 g/mole) tend to have an increased in agglomeration of the polymer particles. The lower molecular weight polymers also tend to have a reduced impact strength when used in a modified PVC composition.
U.S. Pat. No. 5,446,064 (see also European Patent EP 0 618 260 B1) discloses a thermoplastic elastomer composition, comprising the following: (a) 100 parts by weight of a crystalline chlorinated polyethylene, with a chlorination degree of from 20 to 45 percent, and a heat of crystal fusion of from 5 to 35 cal/g, as measured by a DSC method, and obtained by chlorinating a polyethylene having a weight average molecular weight of from 100,000 to 750,000; (b) from 1 to 100 parts by weight of a crystalline polyolefin; and (c) from 5 to 200 parts by weight of a plasticizer.
A 5 cal/g heat of crystal fusion corresponds to a residual HDPE crystallinity in a range from 9-13 percent (as determined by calculations as described for present invention), corresponding to “20 wt percent Cl” to “45 wt percent Cl,” based on the weight of the CPE.
U.S. Pat. No. 4,767,823 (see also EP 0 204 816 B1 and WO86/03499) discloses 25 a halogenated polyethylene resins and halogenated ethylene polymer resins having a reduced tendency to “block.” The halogenated resins are prepared respectively from polyethylene and ethylene polymer starting materials, which have a weight-based median particle size from 120 to 600 microns, and a weight-based particle size distribution, such that more than 60 percent of the particles have a particle size from 30 130 to 850 microns. The halogenated resins also have a weight-based median particle size from 200 to 900 microns. The halogenated polyethylene resins have a chemically combined halogen content from 26 to 42 weight percent, whereas the halogenated ethylene polymer resins have a chemically combined halogen content from 15 to 28 weight percent. The halogenated ethylene polymer resins are prepared from ethylene polymer starting materials, which have polymerized therein, up to five weight percent of 1-olefin monomer copolymerizable with ethylene. In the experimental examples, a considerable amount of chlorine is added at high temperatures, greater than, or equal to, 110° C., as opposed to during the initial, lower, reaction temperatures, favoring a random chlorine distribution.
U.S. Pat. No. 6,706,815 discloses improved polyvinyl chloride compositions having excellent impact strength. In particular, the impact resistant composition comprises the following: a) a vinyl chloride polymer, b) at least one ethylene/alpha-olefin copolymer, said copolymer having a density from 0.858 to 0.91 g/cc and having a melt index from an I10 value of 0.1 to an I2 value of 10, and c) at least one randomly chlorinated olefin polymer having a chlorine content of from 20-40 percent by weight, the feedstock for said chlorinated olefin polymer having a melt index from an I10 value of 0.1 to an I2 value of 10. Optionally, these impact resistant polyvinyl chloride compositions may have inorganic filler levels from 5 to 50 parts per hundred, relative to the polyvinyl chloride polymer.
U.S. Pat. No. 4,029,862 discloses olefin polymer chlorination products having improved handling properties, and which are prepared by reacting, in a fluidized-bed state, certain free-flowing, high bulk density linear olefin polymer powders with gaseous chlorine. The olefin polymer powder used, is characterized by having a flowability, measured as angle of repose in the range of from 24° to 28°, a bulk density in the range from 25 to 35 pounds/cubic foot, and a surface area in the range from 2 to 4 square meters/gram. The individual particles of the olefin polymer particle are characterized by having particle sizes predominantly in the range from 300 to 600 microns, and porosity sufficient to provide an average free volume, within individual particles, in the range from 20 to 45 volume percent, based on total particle volume. In the examples, the chlorination temperature is maintained below 100° C. to prevent the agglomeration of polymer particles and to prevent loss of particle porosity, which affects the chlorination rate. At such low temperatures, the resulting chlorinated polymers have relatively high residual crystallinity.
U.S. Pat. No. 6,204,334 (see also U.S. Pat. Nos. 6,313,229; 6,124,406; EP 1 084 158 B1; and WO 99/50316) discloses blocky chlorinated polyolefins with high crystallinities for use as compatibilizers for PVC and/or CPVC resins with polyolefin elastomers. The blocky chlorinated polyolefins facilitate the dispersion of the elastomers, as a dispersed phase, with the proper size for impact modification of the PVC and/or CPVC. The blocky chlorinated polyolefin are disclosed as providing the following properties: better adhesion between the elastomer and the PVC and/or CPVC; better physical properties, such as impact strength as measured by Notched Izod; and better variable height impact testing (VHIT), as compared to randomly chlorinated polyolefins, often used as processing aids and as impact modifiers in PVC or CPVC. The differences in properties achieved with blocky chlorinated polyolefins versus randomly chlorinated polyolefins are attributed to the individual blocks of the blocky polyolefin being compatible (and/or co-crystalizable) with either the polyolefin elastomer or the PVC/CPVC, resulting in better adhesion between phases.
U.S. Pat. No. 6,277,915 discloses highly crystalline block chlorinated polyolefins for use as performance enhancer of high rubber graft copolymers or chlorinated polyethylenes impact modifier in PVC and/or CPVC resins. The block chlorinated polyolefins (for example, block chlorinated polyethylene) are disclosed as providing good dispersion of the impact modifier particles in the matrix, and better adhesion between the impact modifier and the PVC and/or CPVC interface, providing better physical properties, such as impact strength, as measured by Notched Izod, than did the randomly chlorinated polyolefins, often used as processing aids and as impact modifiers in PVC or CPVC. The differences in properties achieved with block chlorinated polyolefins versus randomly chlorinated polyolefins are disclosed as being attributed to the individual blocks of the blocky polyolefin being compatible with either the impact modifier or the PVC/CPVC, resulting in better adhesion between phases.
Additional block chlorinated polyolefins are disclosed in U.S. Pat. No. 6,780,907.
There remains a need for chlorinated ethylene polymers that can be used in bulk quantities, and can be shipped and stored in bulk quantities, without significant blocking, or massing of the polymer. There is a further need for chlorinated ethylene-based polymers that can be “bulk handleable” without the addition of large amounts of one or more antiblocking agents. There is also a need for chlorinated ethylene polymers that have good processibilty and dispersion in rigid PVC formulations, that result in low or no surface defects, and that provide good impact resistance in the final fabricated product. These needs and others have been met by the following invention.